... volatile acids and alco-hols to substrates such as acetic acid or acetate (CH3COOH) and hydrogen gas thatcan be used by methane-forming bacteria. The third and final stage of the process,methanogenesis, ... (from arachae meaning “ancient”) (Figure 3.4).The domainthrives in heat. Archaebacteria comprise all known methane-forming bacteria, theextremely halophilic bacteria, thermoacidophilic bacteria, ... with respectto the substrates utilized by each group. These groups include the acetate-forming(acetogenic) bacteria, the sulfate-reducing bacteria, and the methane-forming bacteria. The acetate-forming...